Process of making resistance devices.



No 848,954. PATENTED APR-'2, 1907.

L. E. BARRINGER. PROCESS OF MAKING RESISTANCE DEVICES.

APPLIOATION FILED FEB. 5, 1906.

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' U u'rnn sTArns- PATENT OFFICE.

LAWRENCE E. BARRINGER, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PROCESS (BF-MAKING RESISTANCE DEVUCES.

Specification of Letters Patent.

Patented. April. 2, i907.

Application filed February 5, 1906. Serial No. 299.447.

1'0 all whom it may concern.-

Be it known that I, LAWRENCE E. BAR- RINGER, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Processes of Making Resistance Devices, of which the following is a specification.

This invention relates to the manufacture of resistancedevioes-such as rheostats, heaters, and the likeand has for its objectthe improvement in the methods of making the same whereby the resistance-conductor may be insulated and embedded in such a manner that it will withstanda high temperature for an extended period without injury, which -will be inexpensive to manufacture and at the same time exceedingly durable and efficient.

In my previous application, Serial No. 274,409, filed May 11, 1905, I have described and claimed a process whereby the insulating material which I propose to use in this case may be produced. In a subsequent case filed under even date withthis application I have disclosed the embedding of electrical conductorsin the insulating compound. While for certain purposes the embedding of the resistance in the material as carried on in the ap plication above referred to is perfectly satisfactory, I have found that for certain other purposes it is convenient to embed an insulating-conductor after the base or support has beenformed-t. e. the conductori s notpressed into the compound during the process of formati on. I have found that by inserting the resistance-coil in a groove in the base which has been prepared and then filling the groove and the interstices of the coil with my insulat ing compound, which is thinned down for the purpose, preferably to about the consistency of cream or thicker, if desired, and then hardening the whole by steam treatment a very cheap, durable, and efficient resistance device may be produced.

In carrying out my invention in one of its forms I produce a rheostat by pressing the base therefor from my insulating material and having the base prefer-ably grooved, so as to admit a resistance-coil. This base may either be hardened by steam before the coil is inserted therein or after, as is desired. Generally it will be sufficient to insert the resistance-coil in the base, fill inwith the fluid insulation, and after drying treat with the steam,

thereby hardening the device at one treatment. In certain other cases, however, owing perhaps to intricate shape of the base, which might be broken, it may be molded and steam-hardened and then again treated after the coil is inserted. A rheostat made.

up in this way will stand a red heat for a long interval without injury and likewise sudden change of temperatureas, for instance, it may be plunged inwater while at a high temperature without destroying or even rupturing the same. Heating devices may also be made up from this material, the base not necessarily being composed of insulating material, the principal feature being that the coil is embedded'in the insulation without being pressed into it and then steam-hardened.

' In the accompanying drawings I have shown two embodiments of my invention; but it should be understood that these devices are intended merely to illustrate two of the possible forms which my invention may assume, and I wish it to be understood that I do not limit my invention to these specific types of devices nor to the material used, since various modifications as to the arrangement of parts and materials which are withinv the spirit of my invention will suggest themselves to those skilled in the art.

Referring to the drawings, Figure 1 is a plan view of a rheostat-base made in accordance with my invention. Fig. 2 is a sectional View thereof. Fig. 3 is a plan view of the rheostat after the resistanceconductor has been embedded therein and showing the controlling-arm. Fig. 4 is a sectional view thereof. Fig. 5 is a plan view of a heater made in accordance with my invention before the resistance is embedded. Fig. 6 is a sectional view thereof. Fig. 7 shows my heater completed by embedding the resistance and Fig. 8 is an elevation thereof, partly in section.

The construction and .arrangement of the device shown in Figs. 1' to 4 willbe clear from the foregoing description. The base 10 is pressed into the form shown, having the.

hydrate and flint or silica. ()ther materials, such as magnesium hydrate or magnesium oxid, may be used, it being only essential that a substance be employed which will combine with silica to form a silicate under steam treatment. It is preferable in mixing materials to be combined in this manner that amounts corresponding with the molecular proportions be used, the approximate formula of the silicate formed being CaOSiO ZSI-I O,

' the percentage of water varying someadds to thestrength.

so, with my insulating material 16.

what. For instance, when slaked lime and flint are 'used in the proportion of seventyfour to sixty there will be no excess of either lime or flint. The exact proportionsof these materials may be varied, however, throughout a considerable range, and I have found that for certain classes of work the proportions of forty per cent. asbestos, thirty-eight per cent. flint, and twentytwo per cent. calcium hydrate give very satisfactory results. If desired, the fibrous material may be omitted; but its presence These ingredients after being thoroughly mixed and moistened are molded into the desired form under a pressure sufficient to give a densely-compressed body. This base may then be steam-hardened at this stage of the process or not, as desired, although in certain cases,

as Where the base is of intricate form, it may be necessary to harden it before further handling. The resistance-coils 14 and 15 are then inserted in the grooves 11 and 12, respectively, and the grooves filled, or nearly This material 16 is of substantially the same character as that of the base 10, with the exception that the fibrous material is omitted, and it is thinned down so that it can be easily poured or at least laid into the grooves and interstices of the coil without compression. It possesses the same qualities as the material of the base, in that it will be consay about five hours.

applied to a heating device.

verted into a silicate under steam treatment. When the coil is embedded in the base by means of the material 16, the whole is placed under steam treatment for a suitable period I have found that a pressure of one hundred and fifty pounds, corresponding to a temperature of 181 Centigrade, will be sufficient to harden the material in the time above mentioned. The coils 14 and 15 are arranged so that they are above the surface of the base, and a controlling-arm 17, provided with .an operatinghandle 18, is provided for engaging the coils to vary the resistance.

In Figs. 5 to 8 I have shown my invention In this case the base 19 may be made of metal enameled or not, as desired. The base is made dish-.

other insulating material is placed upon the bottom thereof. A spiral coil 21 is laid upon the insulation, the turns of the spiral being insulated from each other by the strips of mica 22, which in some cases may he omitted to allow the compound to run down between the coils, while the binding-posts 23 and 2 1 forni the terminals of the spiral. The base or receptacle 19 is now filled with my insulating material, so that the coil is completely embedded, as shown in Figs. 7 and S. The device is then treated. with steam, as above described. I

It will be seen from the foregoing that I have provided a method of producing rheo stats and heaters which is exceedingly valuable, especially in cases Where for various reasons it would notbe practicable to press the conductors into the material. When har- 'dened, the whole device becomes like slate or soapstone and may be heated to a high tem perature and suddenly cooled without injury. The material, moreover, lends itself readily to various formations by molding and may also be easily machined.

In the foregoing I have set forth in accordance with the patent statutes certain methods of carrying out my invention, while the invention itself and the scope thereof will be indicated in the claims annexed hereto.

I/Vhat Iclaim as new, and desire to secure by Letters Patent of the United States, is-

1. The process of making a resistance device whieh consistsin forming a base from a material which will harden under steam treatment, mounting a resistance-coil in said base, applying a quantity of saidmaterial in a more fluid form to said coil and base and finally hardening the whole with steam.

2. The process of making a resistance device which consists in forming a base from a material which will be converted into a silicate by steam, mounting a resistance-coil in said base, applying a similarly-convertible material in a more fluid form to the coil to secure it in place and treating the whole with steam.

3. The process of making a resistance device which consists in pressing a grooved base from a compound which Will be converted into a silicate by steam, inserting a re.

shaped, as shown, and a layer of mica 20 or 1 with silica and ahydrate,placing a resistance- IIO coil in the groove, filling said groove with a fluid compound of silica and a hydrate and subjecting the whole to steam treatment. 6. The process ofmaking a resistance device which consists in placing a resistance coil'in a suitable base, filling the interstices of said coil with a compound of silica and a hydrate and-subjecting the whole to steam I treatment.

The process of making a resistance device which consists in forming a grooved base 7 from a compound of.a fibrous material with hydrous silicate of calcium, mounting a resistance-conductor in said groove, filling the groove with a compound of silica and a hy- 15 drate and subjecting the whole to steam treatment. 7

In witness whereof I have hereunto set my hand this 2d day of February, 1906.

LAWRENCE E. BARRINGER.

\ Witnesses:

BENJAMIN B. HULL, HELEN ORroRn. 

